Method of producing titanium



Aug 5 1958 w. H. KELLER l ETAL e .2,846,303

f METHOD oF PRobucTNG TITANIUM Filed Aug. ll, 1953 2 Sheets-Sheet 1 TC24 l Reducing Agenl. (e.g. No) l l loY l Y {if-Soll' (opl'iondl) l/ ,l Produclion of Time 'Relcxlively Shorl'. l Lower Chloride Temp. M.P. of Sall'. l TiCl4- TiC2x w Uniforml Reoclion lo Prevenr` I X- 3 +o 2 Formai'on of Ti Fines. l

can be ,l I2? "'\-Ticzx san (MOHM) Single Reac'l'or l Final Lower Chloride Temp.) M.P. of Soll'.

Hzo Acad ITi Ingof or Caslng FIG. l

` INVENTORS W07 me H. Kel/v, l

ATTORNEY.

Aug. 5, 1958 w. H. KELLER ETAL 2,846,303

METHOD 0F PRoDUcING TITANIUM 2 Sheets-Sheet 2 Filed Aug. 1l, 1953 :+352 E QSC.

,Ov ON INIVENTOR.;` t H; Quer vATTORNEY United States Patentl METHOD on PnoDUclNG v Wayne H. Keller, Waban, land Irwin S. yZonis, Belmont,` Mass., ass|gnors to National Research Corporation, (lambrldrge, Mass., a corporation of Massachusetts i l Application Augustll, 1953, Serial No'. 373,512

11 Claims. (Cl. 75-84.5)

This invention relates to the production of metals and more particularly to the production of titanium. A principal object of the present invention is to provide an improved process for the manufacture of titanium and alloys thereof.

Another object of the invention is to provide a process of the above type which produces stable crystalsvof titanium. l

Still another object of the invention is to provide a process of the above type which gives crystals of titanium of suticiently large size so that aqueous leaching can be employed to separate the product titanium from the byproduct salt without contaminating the product titanium.

Still another object of the invention is to provide an improved process for making low-cost titanium having a purity comparablefto titanium produced by the iodide process.

ICC

Patented Aug.. V5, 195.78

mously expensive purification procedures so that the y'rer- 1" 'sultant product titanium must be sold at a high'price. `Ad- Other objects of the invention will in part be obvious and will in part appear hereinafter.

The inventionaccordingly comprises the process involving the several steps and the relation and the order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and thelscope of the application of which will be indicated in the claims. i

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

Fig. l is a flow sheet illustrating one preferred embodiment of the'invention; and l f Fig. 2 is a graph illustrating the gradual reduction of valence employed in the specic examples.

The production of titanium metal has recently been the object of an enormous amount of research work by leading industrial concerns throughout the United States and Europe.. Many methods have been proposed for the production of titanium, a number of these methods involving the metallothermic reduction of titanium halides. In particular, the magnesium reduction of titanium tetrachloride has begun to assume considerable commercial importance.

use aliquid metal reducing agent, such as magnesium, have resulted in the production of titanium in a'spongy form containing large quantities of entrapped magnesium, magnesium chloride, and lower chlorides of titanium. So far as is known, the product from such a reaction (often referred to as the Kroll process) is extremely dithcult` Most of the prior art processes which employ ythe rather low-temperature reduction of titanium by the ditionally, even the drastic precautions taken during purilication invariably result in'a product which is not as pure as that produced by the much more expensive iodide process.

In'the present invention advantage is takenof the wellknown ability of the alkali and alkaline earth metals to reduce titanium tetrachloride, for example, totitaniurn metal. This reaction proceeds rapidly at relatively low temperatures (i. e., temperatures von the order of the melting point of the by-product halide). However, in the present invention the reaction conditions are so adjusted that the product titanium consists of large crystals of titanium which can be removed from the reactor as a slurry of crystalline titanium in the molten salt. These crystals have a size sufhciently large as to permit simple leaching with water (containing a small percentage of acid) to dissolve the by-product halide. yThe' size of the individual crystals is such ythat the surface-to-volume ratio is relatively low, thereby preventing contamination of the product due to the presence of surface oxide.A The nature of the product is also such that its surface activity appears to be very low. Additionally, it is preferred that essentially no lower chlorides of titanium exist in the nal product removed from the reactor. Accordingly, the nature of the product and the use of the slightly acid water leach substantially prevent the possibility of appreciable oxidation of the titanium or hydrolysis of any lower ti-` is in such form that, by simple filtration or decantation,`

the great bulk of the by-product salt can be separated from the titanium crystals so that the amount of leaching is kept to a minimum. This is particularly advantageous in those cases where the recycling of an anhydrous salt to electrolytic alkali metal `or alkaline earth metal cells is an integral part of the over-all operation.

In a preferred method of practicing the present .invention, there is provided, in an air-free reduction zone, a mixture of la molten salt and at least one lower ychloride' of titanium, this mixture being essentially free of titanium fines. The lower chloride content of this mixture is then gradually reduced from an average titanium valence of 3 or less to` a Valence of zero. For convenience, this reduction of the lower chlorides is often hereinafter referred trichloride, titanium dichloride, and perhaps a small quan:h

tity of titanium metal.

In understanding the invention it is convenient to consider the average valence state of the total titanium content (free titanium and titanium chlorides) in the nal reduction zone. The initial valence state in the nalreduction zone may be as high as v3 or maybe as low as 2 or lower. From the standpoint of commercial operation, the preferred initial valence state will depend upon'a number of factors. If the titanium chloride charged to the final reduction zone is to be formed by the reduction of titanium tetrachloride with a metallic reducing agent, such as sodium or the like, it is desirable to carry the initial reduction to an average valence state of 2; This initial reduction may be very rapid, if desired, and can take place in a separate reactor feeding a num-` astsos ber of final reduction zones. As far as is known, about the only limitation on the speed of the formation of the mixture of lower halides (so long as the average valence remains as-high as 2) is the `problem .of removal ofheat ,due to the highly exothermicnaturezof the me'tallothermic reduction reaction. It is extremely important, however, that the initial production of'this mixture be carried out so that formation of titanium nes be prevented. Thus, even though the average titanium valence is as high as 2 or above, the mixture can contain a considerable quantity of titanium nes if the mixture is produced under conditions where localizedunbalance in stoichiometry occurs. Accordingly, it is ofpthe utmost importance that the formation of the initial mixture be achieved under the most nearly uniform concentrations of reducing vagent and reducible titanium compound. By titanium fines is meant titanium particles having a size less than about 200 mesh.

Once the initial charge has been fed Vto the final reduction zone, the growth of titanium crystals in the final reduction zone is accomplished by the gradual reduction of the vaverage titanium valence to zero. From the standpoint of simplicity of the apparatus, it is preferred that, during the final reduction period, only the reducing agent be fed. It is also highly desirable that the reduction of the average titanium valence be uniformly slow throughout the reaction mass. Thus, with a large reactor, the reducing agent should be uniformly dispersed throughout the reaction mass. One method of achieving this uniform distribution of the reducing agent (e.g., sodium) is to feed the sodium to the top of the salt bath and permit lthe sodium to diffuse through the bath by dissolving in the salt bath.

It appears desirable to have the final reduction period continue on the order `of one hour and preferably in excess of two hours. This final reduction period may be as long as 3 to 5 hours, although not much is gained by having the final reduction period longer than about 5 hours. It Iappears that the titanium crystal growth takes place in a mixture containing titanium at an average valence state of less than 3 and that maximum growth apparently takes place as the valence state decreases from 2 to zero at a very slow rate.

This titanium crystal growth requires a definite time period, the lower limit of which seems to be on the order of an hour or so, and the upper limit of which is dictated only by economic considerations. It also requires the presence of lower chlorides of titanium (particularly the dichloride), and that reduction of some of the lower chlorides must be taking place during the growth period. This is true even though the average valence state may remain constant. For example, crystal growth can be obtained at a constant average titanium valence state of 1 if a reducing agent and titanium tetrachloride are fed at a constant slow rate to the final reduction zone containing -a fused salt and a mixture of titanium and titanium chlorides having an average valence state of 1 (see Example II, infra). On the other hand, a similar mixture of salt, titanium, and titanium chlorides, having an average valence state of l, when held for a comparable length oftime at a comparable temperature produces much less crystal growth if -a reducing agent is not present. Thus, as mentioned previously, the growth period is preferably one in which reduction of lower chlorides of titanium takes place. There may additionally be present a number of back reactions, such as the reaction .between titanium trichloride and titanium metal, or the reaction between titanium dichloride and titanium tetrachloride. There may also be present some disproportionation of titanium dichloride and trichloride. It is also quite conceivable (although its existence has notbeen established) that titanium monochloride may exist in the system, in at least a transitory form, and may contribute in a significant manner to the crystal growth reaction.

-ln one .preferred method of practicing the invention;

titanium tetrachloride and sodium, for example, are fed to a final reduction zone at a relatively high rate. This nal reduction Zone may have an initial charge of sodium chloride which is m-aintained at a temperature above its melting point. The relative feed rates of the titanium tetrachloride and sodium may be such as to reduce the initially formed charge-in the final reduction zone to an average valence state of 2, for example `(i. e., one mole titanium tetrachloride and 2 moles of sodium are fed to the final reduction zone). After the initial charge has been formed in the final reduction zone, theflow of titanium tetrachloride is stopped, and the feed rate of sodiumis drastically reduced so that the reduction of the titanium from a valence state of 2 to a valence state of zero is achieved over a relatively long period (on the order of 3 hours or so).

Near the end of the final reduction period, the amount of sodiurnnadded to the final reduction -zoneis more than enough to completely reduce all -of `the'residual titanium chlorides in the final reduction zone. During this last portion of the reduction period, agitation may be employed so as to assure that complete intermixy ing of the-finally introduced excess sodium and any residuallower chloride of titanium is achieved. This assures the production of a molten slurry of titanium crystals in salt which is substantially completely free of `lower chlorides of titanium.,

The process, as described above, may take place` as arbatch operation in a single reactor or it may take place in a plurality of sequentially arranged reactors which provide stepwise reduction of the titanium chlorides yin av plurality of separate reduction zones. Equally, the process can be practiced in a single, multiestage reactor wherein the average valence state of the titanium is gradually reduced to .'zero. This multi-stage-reactor-can thus be a long tube into one end of which titanium tetrachloride is fed, the average valence yst-ate of the titanium content being gradually reduced as the titanium chlorides progress along the length of the tube.

Referring now to Fig. lthere is schematically illustrated one Vpreferred method of practicing the present invention. In this particular embodiment titanium tetrachloride is shown as the starting material, and sodium is illustrated as the reducing agent, these two materials being illustrated for simplicity of description only. `Titanium tetrachloride and sodium are fed to a reactor 10 .for producing a mixture of salt and titanium lower chlorides. The mole ratio oftitanium tetrachloride to sodium is preferably about l `to 2 so as to give a mixture of salt and titanium dichloride. If desired, an additional charge of salt may be provided in the reactor 10 so as to provide more salt than is produced by the initial reduction of the titanium tetrachloride. This initial reduction to the dichloride can take place at a relatively rapid rate and is preferably accomplished with agitation of the salt `bath to provide uniformity of mixing of the reactants to produce a uniform dispersion of the dichloride in the salt. i

Where the average valence of the titanium produced inthe first stage reduction is 2 or above, this first stage reduction may take place as rapidly` as the heat can be removed from the reactor. The mixture of salt and lower chlorides of titanium produced in the reactor 10 is fed to a final reduction zone 12 wherein the lower chlorides of titanium are gradually reduced to a valence of zero by slowly introducing two additional moles of sodium into the final reduction zone. This reduction preferably takes place over a time period in Vexcessof an hour, `preferably as long as 3 hours or more.

'Complete reduction of the lower chloride is achieved in the final reduction zone. reduction, it is also preferred thatfsome excess sodium be provided so as to assure complete freedom from lower.

chlorides of titanium.

The resultant slurry of titanium crystals, molten salt,A

After the completion of the- 5 and excess sodium is thensubjected to a separation step 14 which may be a simple decanting operation wherein theiexcesssodium is removed, as a liquid, from the mixf ture.' .Most of the'excess by-product salt may also be drained loi at this point, and a relatively concentrated mixture of titanium crystals and salt may then be transferred4 to an aqueous acid leaching bath, indicated at 16. Itis obvious that the titanium crystals and the salt must be lcooledy prior to the'aqueous acid leaching step. The resultant leached titanium crystals are thendried and preferably fed to an' arc melting operation 18 where they can be formed into an ingot, casting, or the like. Additional alloying elements may be. added tothe titanium during the melting operation.

Numerous modifications' in -the above invention may rbe made without departing from the scope thereof. For `ex ample,'the two reduction operations 10 and 12 can be carried out in a single batch reactor, if desired. Thus, 2 moles of sodium and 1 mole of titanium tetrachloride .may be initially fed into the single reactor at a relatively high ratey of speed. After a desired quantity of titanium dichloride has been so produced, the titaniumtetrachlov ride feed maybe stopped and the sodium supply may be reduce so that the reduction of the dichloride to titanium metal takes place over a time period on the order of several hours. With a properly constructed reactor the decanting and gross separation of the titanium crystals from the bulk of the salt may take place within the single reactor.

3 In order to describe more fully a number of alterna-v tivemethods of practicing the invention, there are set forth below a few specific examples of experimental runs which have been made. These examples are nonlimiting andare merely illustrative of numerous additional embodiments of the invention. In these examples, the experiments were carried out in ay nickel reactor having a diameter of l2 inches and a height of 27 inches. The reactor was equipped with a stirrer for agitating the salt bath in thereactor. Feed tubes were provided for .feeding liquid titanium tetrachloride and liquidv sodium (or yliquid sodium-potassium alloy) vto the reactor; Temperatures werel indicated by thermocouples positioned within the salt charge. An atmosphere ofargon was maintained in :the reactor during the runs.

Example l y 30' lb's. of NaCl were charged to thereactor which was then purged of air by the use of a vacuum and The reactor Was then heated to about 890 C.y

argon. Titanium tetrachloride was fed to the reactor at al rate of 42.8 lbs. per hour along with sodium at a rate of 10.4 lbs. per hour. During this initial reduction of titanium tetrachloride (1 mole of TiCl4 and 2 moles of Na), the

saltv bath was agitated to provide a uniform dispersion of titanium dichloride in the molten salt, and the average temperature of the molten salt was about 910 C. After one hour the feed of titanium tetrachloride was'stopped.

and the feed of sodium was reduced to 2.08 lbs. per hour. This modified feed rate was maintained for 5 hours, the average valence of the titanium dropping during this time from 2 to 0. During this portion of the run the sodium l was fed to the top of the salt bath and no agitation was employed. During the final reduction portion` of the reaction, the temperature of the salt bath was maintained at about 890 C. During the linal reduction (i. e., after formation of the initial titanium dichloride charge), the average over-all titanium production rate was at 3.6 lbs. of titanium per cubic foot of final reduction mixture per hour.

Due to the exothermc nature of the reaction, even at the slow rate of reduction, it was possible (by radiation cooling) to maintain the reactor walls at a temperature' slightly below the melting point (i. e., 800 C.) of the salt. The reactor walls were thus protected by a thin layer of frozen salt. At the termination of the run the total charge in the reactor was allowed to freeze and was cooled to room temperature. Thereafter, the product .was removed` from the reactor and was subjected to leaching in 5% hydrochloric acid. After the acid leaching Ythe product was leached in methanol and then ether and finallyl dried under a vacuum to remove all traces of Water, alcoholj..

and ether.

The titanium crystals produced under the above con-i ditions had a size distribution preponderantly greater than about 20 mesh. Anumber of the 'crystals hada length of l inch or longer, and an average thickness of 1/16 inch. 88% of the resultant titanium crystals were arcamelted in an inert atmosphere to form buttons. These buttons had a Rockwell A hardness of less than 52. Of the total product, 63% (+20 mesh)"had a Rockwell A hardnessy v of 37. The variation of the average titanium valence (onvk reduction reaction isA a cumulative basis) during this plotted in Fig. 2.

Example II 5 l-bs. of a mixture of sodium chloride -and'potasvsium alloy consisted of about'56% sodium and 44% potassium (on a weight basis). `The titanium tetrachloride feed was stopped at the end of 180 minutes and the sodium-potassium feed was continued for a total time of 226 minutes. salt bath was agitated by'use of a stirrer. As will be apparent from the above figures, the initial valence of the titanium formed was 1,' this valence remaining at an average of 1 for the first 3 hours and then being-'slowly reduced to zero during the last 45 minutes. `The product from this run was treated in a manner similar to that of Example I.

plotted in Fig. 2.

Example III An empty reactor waspurged of air and charged withv argon and then heated to about 850 C.' Titanium tetrachloride Was fed to the reactor ata rate of'20.8 lbs. per hour for 14 minutes. During this feed of titanium tetral chloride feed was decreased to 9.67 lbs. per hour. This rate was continued for 82 minutes. The titanium tetrachloride feed was then stopped and the sodium-potassium feed was continued at a rate of 8.53 lbs. per hour for an additional 4l minutes. The run was held at temperature for an additional period of minutes after cessation of the sodium-potassium feed. f During 'this total run no agitation was employed and the temperature of the salt bath Was maintained at about 850 C.

The product from this run was treated in a manner similar to that of Example I. A representative sample was then arc-melted to give a Rockwell A hardness of 37. The average titanium valence during this run is plotted in Fig. 2.

While specific experimental runs have `been illustrated above, numerous alternative methods may be employed without departing from the spirit of the invention. The temperature of the reaction mass may be widely varied from slightly above the melting point of the salt to temperatures on the order of 1000 C. and above.y lHow- During the totalreduction time, the-v A representative samplel was l then arc melted to give a button having a Rockwell A hardness f of 48. The average titanium valence during thisk run is g ever, there appears to be no particular advantage in operating at the higher temperatures and these higher temperatures give increasingly serious problems of materials of construction, heat transfer, etc. Numerous reducing agents, other than the sodium or sodium-potassium alloy, can be employed; 'for example, potassium, calcium, magnesium, lithium, and various combinations of these elements may be utilized. From the standpoint of cheapness, sodium, sodium-potassium alloy, or magnesium are preferred. Other halides of titanium may be utilized, although from the standpoint of cost, ease of handling, etc., the tetrachloride is most preferred.

Additionally, the reactor can be fed with lower halides of titanium such as titanium trichloride manufactured from titanium-bearing materials in the manner shown in the copending applications of Singleton, Serial No. 304,388, filed August 14, 1952, and Singleton, Serial No. 315,461, led October 18, 1952. Equally, titanium trichloride can be made by the technique described by Sherfey et al., lournal of Research of the National Bureau of Standards, 46, 299-300, April 1951. Additionally, the dichloride of titanium can be manufactured by numerous processes such as disproportionati'onof the trichloride or partial reduction of the trichloride or Vtetrachloride.

The present invention can be equally employed for the manufacture of titanium alloys by the co-reduction of the chlorides, for example, of vanadium, chromium, manganese, iron, nickel, cobalt, columbium, tantalum, molybdenum, tungsten, or silicon. In this case thealloyl may be a binary alloy or it may be an alloy containing 3 or 4 constituents. In the manufacture of alloys the same general conditions of the slow reduction of the titanium halide and reducible compounds of the alloying constituents must be employed.

When a continuous reactor is employed, as distinguished from the batch reactor, it is preferred tohave numerous points of introduction of the reducing agent (e. g., sodium) so as to obtain as uniform as possible a distribution of the sodium into the reaction mixture. As pointed out above, it is highly undesirable to provide, in localized zones of the reaction mixture, any amount of reducing agent which is sufficient to rapidly reduce the titanium chlorides to metallic titanium. With the continuous reactor, it is preferred to have a slowlymoving stream (which may be moving in a horizontal direction through a long tube). With such an arrangement of reactor, the reducing agent (e. g., sodium) is introduced at a great many points along the moving stream so that the moving stream is slowly and uniformly reduced from an average valence of less than 3 to a valence of zero in a time period of approximately 3 to 5 hours. Thus, if one mole of titanium tetrachloride is introduced at one end of the tube along with one mole of sodium (to form TiCl3) so that the titanium in the initially formed mixture has an average valence of 3, it will leave the other end of the long tube 3 to 5 hours later at a valence of zero.

In a continuous reactor it is preferred that the hot mixture of molten salt and titanium crystals be discharged onto a chilled surface so as to rapidly freeze the salt ina non-adherent form on the chilled surface, and to rapidly lower the temperature of the contained titanium to a point Where it is not appreciably reactive.

It should be additionally pointed out that the salt mixture in which the slow reduction is carried out may be formed of numerous halides which can be mixed halides, single halides, and halides of materials other than the specific reducing agent or agents employed in the reaction. 'From the standpoint of simplicity of operationl and ease of control, it is preferred, however, that the salt be the chloride of the reducing agent. Thus, while it is quite feasible to employ binary and ternary mixtures of halides having quite low melting points, not too much is gained and the additional expense is not particularly iii) lio

warranted. This is particularly true in View of the excellent results Vwhich can -be obtained by the use of sodium chloride as the salt for supporting the the slurry of titanium dichloride (in a preferred embodiment) which is slowly reduced to titanium metal.

It should be pointed out, in connection with a consideration of the various salts which can be employed, that these salts should be completely anhydrous and free of any contaminants such as carbon, nitrogen, oxygen, or hydrogen. This is due to the tremendous reactivity of titanium metal at temperatures on the order of 800 to 900 C. and above.

In connection with the formation of alloys, the coreduction of alloying halides has been mentioned previously and the addition of alloying elements to the nal titanium crystals in the melting step is shown in Fig. 1. Other alloying methods, such as the formation of master alloys and the like, may be equally employed during the reduction operation or during the subsequent melting operation. When the word titanium is used in the appended claims, it is intended to include alloys as well as the pure metal.

While lthe invention has been described in a preferred form wherein the average titanium valence is taken from a value of 2 or more to zero during the final reduction period, it can be modified -by providing for less than complete Areduction of the titanium chlorides in the final reduction period. Thus, for example, the reduction of a salt-titanium chloride mixture may be slowly reduced from an average valence of 2 to an average valence of about 0.5 over an extended period. Equally, the reduction may be achieved over an extended period at a constarrt average valence of about l (see Example II), without completing the reduction to a valence approaching or equalling Zero. The resultant residual titanium chlorides in the mixture can then be reduced to titanium metal rapidly and in a separate zone. This method is less preferred, however, since rapid reduction of appreciable quantities of titanium chlorides inevitably produces an almost quantitative yields of titanium fines. Such iines are extremely difficult to separate, in a pure state, from the residual salt and unless separated from the larger titanium crystals will add sufficient impurities to the finally melted titanium so as to drastically reduce its value.

Equally, the titanium crystals can be separated from the mixture of titanium crystals, salt and lower chlorides and the crystal-free mixture, with its titanium chloride content, can be recycled to the reactor. This method is also less preferred since it is extremely diliicult to separate the titanium crystals from the mixture of salt and lower chlorides without contaminating the titanium crystals, oxidizing the lower titanium chlorides, or producing large quantities of titanium iines.

Since certain changes may be made in the above process without departing from the scope of the invention herein involved, it is intended that Iall matter contained in the above description, or shown in the accompanying drawings, shall -be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. The process of producing crystalline titanium which comprises the steps of providing a mixture of a molten salt and at least one lower halide of titanium in an airfree reduction zone, said mixture being substantiallyfree of titanium iines, maintaining the salt in the reduction. zone at a temperature above its melting point, introducing a reducing agent into the reduction zone at a relatively slow rate so that the average valence state of the titanium in the reduction zone is gradually reduced, said reducing agent comprising at least one metal selected' from the group consisting of the alkali metals and the alkaline earth metals, the introduction of the reducing agent into the reduction zone being sufficiently gradual to require a reduction period of at least two hours for reducing the average titanium valence from a value of less than 3 to a value of zero, said reducing agent lbeing substantially uniformly introduced into the mixture `to `'eliminate high concentrations of undissolved reducing f agent capable of achieving rapid reduction of the average titanium valence in localized portions of the molten' salt in the reaction zone, and separating the titanium crystals from the salt. I 2. The process of claim 1 wherein the reducing agent comprises sodium and the s'alt comprises sodium chloride.

3. The process of claim 1 wherein the mixture'of salt and lower halides .of titanium is advanced slowly through the reduction zone, the gradual reduction of the average titanium valence in the advancing mixture being achieved by introduction of the reducing agent at spaced points along the path of travel of the mixture.

4. The process of claim 1 wherein the mixture of salt and lower halides of titanium is formed in the reduction z one by initially introducing titanium tetrachloride and an amount of reducing agent less than that required for Y complete reduction of the introduced titaniumtetrachloride,.the relative rates of introduction of vthe tetrachloride and the reducing agent being shifted to achieve the igradual reduction of the average titanium valence to zero. 5. The process of claim 1 wherein the salt comprises a' halide of one vof the metals from the groupl consisting of the alkali metals and the'alkaline earth metals.

'i 6. The process of claim 1 wherein the saltis a chloride of thereducing agent.

7. The process of claim 1 wherein the uniform introduction of the reducing agent into the salt is obtained by dissolving the reducing agent in the salt.

8. The process of claim 1 wherein a halide of an alloying metal is slowly reduced along with the halide of titanium Vto provide crystals of titanium containing said alloying metal.

9. The process of claim 1 wherein the halide of titanium comprises a lower chloride of titanium and a chloride of titanium is introduced into the reductionj zone during the reduction of the lower titanium chloride. 'l i 10. In a process for producing titanium whereina lower halide of titanium is dissolved in "a fused salt bath which is substantially free of titanium lines and the titanium halide is slowly reduced to titanium crystals over an extended period of `at least one hour yby means lof af met-allie reducing agent, the average titanium valence decreasing from a value of between two and three to a value approaching zero during the reduction period, the 'metallie reducing agent comprisingat least one metal se'- lected from the group consisting of the alkalifmetalsy and the alkaline earth metals, the improvement which comprises adding molten reducing agent to the surfaceofthe fused salt bath over an extended period of time While` said bath remains quiescent.

l1. The process of claim 10 wherein the` halide of titanium comprises titanium dichloride dissolved in a fused `sodium chloride bath and the reducing agent comprises sodium. v

References Cited inthe file of this patent UNITED kSTATES PATENTS f 4OTHER REFERENCES Zeitschrift fr Anorganische und Allegemeine Chemie,

vol. 234, 1937, pages 42-50. Page 44 pertinent.

Report of Investigations 4519, Production ofDuctile Titanium at Boulder City, Nev. Published August 1949 by Bureau of Mines, Washington, D. C. Pages 9-14 pertinent. Entire report 39 pages. v i Y Journal of Metals, April 1950, pages' 634-640. 

10. IN A PROCESS FOR PRODUCING TITANIUM WHEREIN A LOWER HALIDE OF TITANIUM IS DISSOLVED IN A FUSED SALT BATH WHICH IS SUBSTANTIALLY FREE OF TITANIUM FINES AND THE TITANIUM HALIDE IS SLOWLY REDUCED TO TITANIUM CRYSTALS OVER AN EXTENDED PERIOD OF AT LEAST ONE HOUR BY MEANS OF A METALLIC REDUCING AGENT, THE AVERAGE TITANIUM VALENCE DECREASING FROM A VALUE OF BETWEEN TWO AND THREE TO A VALUE APPROACHING ZERO DURING THE REDUCTION PERIOD, THE METALLIC REDUCING AGENT COMPRISING AT LEAST ONE METAL SE- 